The present invention relates to apparatus for reading information recorded in a memory layer, such as an X-ray memory layer and an X-ray cassette and X-ray table for use with the apparatus.
Particularly for medical purposes, an image of an object (such as a patient) is created using X-ray radiation that is recorded in a memory layer as a latent image. A phosphor film base is often used for this memory layer. In order to read the X-ray image recorded in the memory layer, the memory layer is excited using a radiation source. Because of this excitation, the memory layer radiates light of an intensity corresponding to the recorded X-ray image. The light emitted from the memory layer is received by a receptor and eventually converted into electrical signals so that the X-ray image recorded in the memory layer may then be made visible. The X-ray image may, for example, be displayed directly on a monitor or printed onto a special X-ray film suitable for X-ray images.
Such a device used to read out information recorded in a memory layer is known, for example, from published International Patent Application No. WO 99/28765. In this known device, the memory layer is excited by rows by an exciter beam that is created by a radiation source. This radiation source may be a laser diode strip, for example. The light emitted because of excitation of the memory layer is received by a receptor. For this purpose, the receptor contains a number of light-sensitive surfaces that are arranged in adjacent rows. The radiation emitted from the memory layer is received by the light-sensitive surfaces. The receptor may be a Charge-Coupled Device (CCD) that contains a number of photo-detectors arranged in adjacent rows.
In order to read the information recorded in the memory layer, the radiation source and receptor are moved over the memory layer by means of a linear motor.
Based on the principle advanced by the aforementioned publication No. WO 99/28765, the principal objective of the present invention is to provide a simple and effective means to improve the quality of reproducing information recorded in a memory layer.
This objective, as well as other objectives which will become apparent from the discussion that follows, are achieved, in accordance with the present invention, by providing apparatus for reading information stored in a memory layer which includes a reader device having a receptor to receive emission radiation that contains an image of the information recording on the memory layer. The apparatus also includes a shielding device, which serves to shield the reader device from an information recording beam. Alternatively or additionally, it is possible to provide a converter that serves to convert an information recording beam into converted radiation that possesses less energy than the information recording beam.
As a result of the invention, impact of high-energy storage radiation on the reader may be avoided. The reader contains semiconductor components that are sensitive to the energy-rich recording radiation. As a result of the invention, it is possible to prevent, or at least reduce, the formation of grid error points within these semiconductor components. Such grid error points can cause alteration of the specific characteristics of the semiconductor components after cumulative irradiation from the recording beam. Specific characteristics of these semiconductor components may be altered by increasing levels of radiation exposure frequency by means of recording radiation. Aging symptoms may appear in these semiconductor components that then may lead to a negative effect on image quality during reproduction of the information recorded. The signal-to-noise ratio during reproduction of the information recorded is worsened. This is prevented by the invention.
In an advantageous embodiment of the invention, the shielding device that shields the reader from storage radiation contains lead in order to prevent impact of the recording radiation on the reader. This allows shielding mainly against X-rays used as recording radiation in a simple and effective manner.
In a further advantageous embodiment of the invention, the converter according to the invention used to convert the recording radiation into a beam that is of reduced energy with respect to its energy content also performs a wavelength conversion. Thus, for example, an X-ray beam may be transformed into a wavelength band that is located within the visible spectrum, particularly in the blue or ultra-violet range.
In a further particularly advantageous embodiment of the invention, the shielding device or conversion device is arranged above the resting position of the reader. Thus, the size of the shielding device or conversion device may be limited. Further, a fixed position is assigned to the shielding device or conversion device within the apparatus according to the invention. It is thereby ensured that the reader is protected from the high-energy recording beam during downloading of information in the memory layer.
Advantageously the reader device, shielded by the shielding device or conversion device, also contains a radiation source to excite the memory layer. This radiation source with the receptor is therefore simultaneously shielded from the recording beam.
For a full understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention as illustrated in the accompanying drawings.